Vehicle behavior calculation device

Abstract

To provide a vehicle behavior calculation device capable of calculating a lateral velocity of a vehicle with a simple algorithm.SOLUTION: A calculation device 14 calculates a lateral velocity at an axle center of rear wheels of a vehicle by multiplying a product of a lateral angle of the vehicle detected by an IMU 26 and a longitudinal speed of the vehicle detected by a vehicle speed sensor 24 by a proportionality coefficient which is an inverse number of a product of a normalized cornering stiffness of the rear wheels, a gravitational acceleration, and -2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle behavior calculation device, and more particularly to a vehicle behavior calculation device capable of calculating a lateral speed of a vehicle using a simple algorithm. [Background technology]

[0002] When estimating vehicle motion, it is necessary to calculate the vehicle's longitudinal speed, lateral speed, and vehicle body slip angle. If we assume that the vehicle is a rigid body, then of the six degrees of freedom of motion of a rigid body, the longitudinal speed can be measured by a vehicle speed sensor, the roll angle and pitch angle by an IMU (inertial measurement unit), and the azimuth angle by a GPS. In addition, the vertical speed of a moving vehicle is zero, so no measurement is required. However, since the lateral speed and slip angle cannot be directly measured by sensors, various estimation methods have been proposed.

[0003] A typical estimation method is to estimate the vehicle mass and center of gravity based on steering angle data, and physical parameters such as front and rear tire cornering stiffness, etc. This method requires a large number of physical parameters, and further requires parameter adjustment for estimation calculations, and there is a problem that the estimation result depends on the accuracy of each physical parameter.

[0004] In addition, there have been cases where a Kalman filter or the like is used to estimate the lateral speed of the vehicle by repeatedly comparing a predicted value estimated from an observed value detected by a sensor or the like with a new observed value to increase the accuracy of the predicted value. However, there has been a problem in that the calculation process of an algorithm such as the Kalman filter is complicated, and it is not easy to quickly calculate the lateral speed of the vehicle.

[0005] Patent Document 1 discloses an invention of a vehicle physical quantity estimation device that estimates a roll angle of a vehicle from a vehicle speed, yaw rate, and lateral acceleration detected by sensors, and estimates the lateral speed of the vehicle using the estimated roll angle and a steering angle sensor value.

[0006] Patent Document 2 discloses an invention relating to a vehicle slip angle estimation method that estimates the longitudinal speed and lateral speed of a vehicle by integrating the value of an acceleration sensor over time, and also estimates the slip angle of the vehicle. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2008-94375 A [Patent Document 2] JP 2006-256469 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the invention described in Patent Document 1 has a problem in that the accuracy of the estimated lateral velocity depends on the accuracy of the estimated roll angle, and also has a problem in that a separate steering angle sensor is required.

[0009] The invention described in Patent Document 2 integrates the acceleration sensor value over time, but has the problem that the value is prone to divergence due to the influence of bias, and the accuracy is poor in the normal range.

[0010] The present invention has been made in consideration of the above problems, and has an object to realize a vehicle behavior calculation device that can calculate the lateral speed of a vehicle using a simple algorithm. [Means for solving the problem]

[0011] The vehicle behavior calculation device of the first aspect includes an acceleration detection unit capable of detecting lateral acceleration at the center of the rear wheel axle of the vehicle, a vehicle speed detection unit that detects longitudinal speed at the center of the rear wheel axle, and a calculation unit that calculates the lateral speed at the center of the rear wheel axle by multiplying the product of the lateral acceleration detected by the acceleration detection unit and the longitudinal speed detected by the vehicle speed detection unit by a predetermined proportionality coefficient.

[0012] In the first aspect, the lateral speed at the center of the rear wheel axle of the vehicle is calculated based on the fact that the lateral speed at the center of the rear wheel axle is proportional to the product of the lateral acceleration detected by the acceleration detection unit and the longitudinal speed detected by the vehicle speed detection unit.

[0013] In a second aspect, in the first aspect, the calculation unit multiplies the lateral acceleration detected by the acceleration detection unit by the predetermined proportionality coefficient to calculate a slip angle at the center of a rear wheel axle of the vehicle.

[0014] In the second aspect, the slip angle at the center of the rear wheel axle of the vehicle is calculated based on the fact that the slip angle at the center of the rear wheel axle is proportional to the lateral acceleration detected by the acceleration detection unit.

[0015] A third aspect is the first or second aspect, wherein the predetermined proportionality coefficient is the inverse of a product of the normalized cornering stiffness of the rear wheels, the acceleration of gravity, and −2.

[0016] The proportionality coefficient common to the slip angle at the rear wheel axle center of the vehicle and the lateral speed at the rear wheel axle center of the vehicle is calculated by the normalized cornering stiffness that does not depend on the vehicle mass and the gravitational acceleration. The lateral speed at the rear wheel axle center of the vehicle can be easily calculated by simply multiplying the proportionality coefficient by the lateral acceleration that can be detected by an IMU or the like and the wheel speed that can be detected by a vehicle speed sensor.

[0017] In a fourth aspect, in the first or third aspect, the acceleration detection unit is capable of detecting a roll rate and a yaw rate, which are angular accelerations of the attitude angle of the vehicle, and the calculation unit calculates the lateral velocity at the rear wheel axle center by adding the product of the yaw rate detected by the acceleration detection unit and a coordinate value of the vehicle in the longitudinal direction from the rear wheel axle center at an arbitrary position on the vehicle to the lateral velocity at the rear wheel axle center, and subtracting the product of the roll rate detected by the acceleration detection unit and a coordinate value of the vehicle in the vertical direction from the rear wheel axle center at the arbitrary position.

[0018] In the fourth aspect, the lateral velocity at any position on the vehicle can be calculated by adding or subtracting values ​​related to yaw rate and roll rate that can be detected by an IMU or the like to the lateral velocity at the center of the rear wheel axle.

[0019] A fifth aspect is the second or third aspect, wherein the acceleration detection unit is capable of detecting a roll rate and a yaw rate, which are angular accelerations of an attitude angle of the vehicle, and the calculation unit calculates the slip angle at the rear-wheel axle center by adding a value obtained by dividing the product of the yaw rate detected by the acceleration detection unit and a longitudinal coordinate value of the vehicle from the rear-wheel axle center at an arbitrary position on the vehicle by the longitudinal speed detected by the vehicle speed detection unit, and subtracting a value obtained by dividing the product of the roll rate detected by the acceleration detection unit and a vertical coordinate value of the vehicle from the rear-wheel axle center at the arbitrary position by the longitudinal speed detected by the vehicle speed detection unit, to the slip angle at the rear-wheel axle center.

[0020] In the fifth aspect, the lateral speed at any position of the vehicle can be calculated by adding or subtracting values ​​related to the yaw rate and roll rate that can be detected by an IMU or the like to the slip angle at the center of the rear wheel axle. Effect of the Invention

[0021] According to the present invention, it is possible to realize a vehicle behavior calculation device capable of calculating the lateral speed of a vehicle using a simple algorithm. [Brief description of the drawings]

[0022] [Figure 1] 1 is a block diagram showing an example of a vehicle behavior calculation device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating a coordinate system according to an embodiment of the present invention. [Diagram 3] FIG. 4 is an explanatory diagram showing an example of a variable in the embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram of a slip angle. [Diagram 5]FIG. 2 is a block diagram showing an example of an input / output relationship of a calculation device according to an embodiment of the present invention. [Figure 6] FIG. 11 is an explanatory diagram showing the relationship between the longitudinal speed and lateral speed at the center of gravity of the vehicle, the longitudinal speed and lateral speed at the center of the rear axle, the distance from the center of gravity to the center of the front axle, the distance from the center of gravity to the center of the rear axle, the front tire lateral force, and the rear tire lateral force. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in Fig. 1, a vehicle behavior calculation device 10 according to this embodiment includes a storage device 18 that stores data necessary for the calculation of the calculation device 14 and the calculation results by the calculation device 14, an input device 12 to which the vehicle longitudinal speed detected by a vehicle speed sensor 24 and the angular velocity and acceleration of the attitude angle of the vehicle detected by an IMU 26 are input, the calculation device 14 that performs calculations to estimate the lateral speed, slip angle, etc. of the vehicle based on the input data input from the input device 12 and the data stored in the storage device 18, and an output device 16 that outputs the lateral speed, slip angle, etc. of the vehicle calculated by the calculation device 14.

[0024] Next, a coordinate system related to the behavior of the vehicle 200 is defined as shown in FIG. 2. The Earth coordinate system 204 is based on the Earth plane and has the direction of gravitational acceleration and z e and are parallel, and y e The vehicle body coordinate system 208 is a coordinate system fixed on the vehicle body springs, and z v is the vertical upward direction of the vehicle body, x v faces the vehicle travel direction. Therefore, the front-rear direction of the vehicle 200 is a direction parallel to the x-axis of the vehicle body coordinate system 208. As will be described later, in this embodiment, the reference point of the vehicle body coordinate system 208 is not the center of gravity of the vehicle 200 but the center of the axle of the rear wheels of the vehicle 200 in the vehicle width direction. Also, in this embodiment, the vehicle body coordinate system 208 is used, and the earth coordinate system 204 is not used.

[0025] Moreover, the roll angle φ, pitch angle θ, and yaw angle ψ, which are Euler attitude angles, are defined with respect to the Earth coordinate system 204 as shown in Fig. 2. For example, the roll angle φ is a rotation angle around the x-axis, the pitch angle θ is a rotation angle around the y-axis, and the yaw angle ψ is a rotation angle around the z-axis. Moreover, each of the roll angle φ, pitch angle θ, and yaw angle ψ indicates a positive value when rotating in the direction of a right-hand screw (the direction of each arrow in Fig. 2). In this embodiment, hereinafter, when simply referring to the roll angle φ, pitch angle θ, and yaw angle ψ, this basically refers to the roll angle φ defined with respect to the vehicle body coordinate system 208. v , pitch angle θ v and yaw angle ψ v Let us assume that.

[0026] FIG. 3 is an explanatory diagram showing an example of variables in this embodiment. In this embodiment, the longitudinal speed V x , the lateral speed V of the vehicle 200 y and the vertical speed V of the vehicle 200 z Define each of V x is the x-axis, V y is the y-axis and V is z are each parallel to the z-axis.

[0027] The output values ​​of the IMU 26 corresponding to the roll angle φ, pitch angle θ, and yaw angle ψ of the vehicle 200 are defined as a roll rate P, a pitch rate Q, and a yaw rate R, which are angular velocities.

[0028] As shown in FIG. 3, in the vehicle body coordinate system 208, the velocity vector is v=(V x , V y , V z ), angular velocity vector ω = (P, Q, R), force vector F = (F x , F y , F z )

[0029] Fig. 4 is an explanatory diagram of slip angle β. The direction of tire center line 110 and the traveling direction 112 of tire 100 intersect at the rotation axis 102 of tire 100, but when the vehicle is turning, the direction of tire center line 110 and the traveling direction 112 of tire 100 usually do not coincide. As shown in Fig. 4, when tire 100 is viewed from, for example, the z-axis direction of earth coordinate system 204, the angle β between the direction of tire center line 110 and the traveling direction 112 of tire 100 is called the slip angle or sideslip angle.

[0030] The slip angle is defined as above, but as will be described later, in this embodiment, the slip angle β is defined as a quotient of the lateral speed of the vehicle as the dividend and the longitudinal speed of the vehicle as the divisor.

[0031] The principle of calculating the lateral speed and slip angle of the vehicle will be described below.

[0032] 5 is a block diagram showing an example of an input / output relationship of the arithmetic device 14 according to the present embodiment. The arithmetic device 14 according to the present embodiment calculates the vehicle body lateral speed based on the vehicle speed detected by the vehicle speed sensor 24 and the vehicle lateral acceleration detected by the IMU 26.

[0033] FIG. 6 shows the longitudinal velocity x at the center of gravity CG of the vehicle 200. c and lateral velocity y c , the longitudinal velocity x at the rear wheel axle center 202 w and lateral velocity y w , the distance l from the vehicle center of gravity CG to the front wheel axle center 210 f , the distance l from the vehicle center of gravity CG to the rear wheel axle center 202 r , Front tire lateral force F f , rear tire lateral force F r FIG.

[0034] If the mass of the vehicle 200 is m, the roll angle, which is a road surface attitude angle, is φ, and the pitch angle, which is also a road surface attitude angle, is θ, the lateral motion equation at the center of gravity CG of the vehicle 200 is expressed by the following equation (1). c,y is the lateral acceleration at the vehicle's center of gravity (CG). JPEG0007669820000001.jpg14148

[0035] In addition, if the vehicle body moment of inertia around the vehicle center of gravity CG is I and the vehicle body yaw rate is R, the rotational equation of motion is expressed as the following formula (2). The left side of formula (2) is the product of the vehicle body moment of inertia I and the time differential of the vehicle body yaw rate R, and the right side of formula (2) is the distance l from the vehicle center of gravity CG to the front wheel axle center 210. f and front tire lateral force F f From the product of these, the distance l from the center of gravity CG of the vehicle to the rear wheel axle center 202 is r and rear tire lateral force F r This indicates that the product of is subtracted. JPEG0007669820000002.jpg15117

[0036] In this embodiment, since the behavior of the vehicle 200 in a normal range during daily driving is assumed, rather than the extreme behavior of the vehicle 200 in sports driving, it is assumed that the rotational acceleration, which is the time derivative of the vehicle body yaw rate R, is approximately 0. With this assumption, the following equation (3) is obtained from the above equation (2). JPEG0007669820000003.jpg22117

[0037] By substituting the above equation (3) into equation (1), we obtain the following equation (4). JPEG0007669820000004.jpg21155

[0038] The wheelbase l of the vehicle 200 is l=l f +l r Therefore, the following equation (5) can be obtained from equation (4). JPEG0007669820000005.jpg21134

[0039] In addition, the vertical load m at the rear wheel position r g is m r g = (l f / l) mg, the following equation (6) can be obtained from equation (5). JPEG0007669820000006.jpg14134

[0040] In the linear region where the tire lateral force is proportional to the slip angle, the rear tire lateral force F r is expressed by the following formula (7). In formula (7), C r is the normalized cornering stiffness obtained by dividing the cornering stiffness by the wheel load, and V c,y , V c,x are the lateral and longitudinal speeds at the vehicle's center of gravity CG, respectively. JPEG0007669820000007.jpg22119

[0041] Based on the above equations (1) to (7), the following equation (8) is obtained. JPEG0007669820000008.jpg22164

[0042] In transforming the above equation to the center of the rear wheel axle, we consider three position vectors. Vector r from the origin of the Earth coordinate system to the center of the rear wheel axle ew , vector r from the origin of the Earth coordinate system to the center of gravity CG of the vehicle ec , vector r from the vehicle center of gravity CG to the rear wheel axle center 202 cw Considering this, the relationship shown in the following equation (9) holds. JPEG0007669820000009.jpg1295

[0043] By differentiating the above equation (9) with respect to time, we obtain an equation for converting the velocity at the center of gravity CG of the vehicle into the velocity in the Earth coordinate system. The time differentiation of equation (9) is the rotational angular velocity ω c and the rotational angular velocity ω at the rear axle center v Since the values ​​of dr / dt are the same, the relationship dr / dt = δr / δt + ω × r is used to rearrange the equations as follows. cw indicates the relative position from the center of gravity CG of the vehicle to the rear wheel axle center 202, and r cw =(l x , l y , l z ). JPEG0007669820000010.jpg106164

[0044] In addition, V w =dr ew By differentiating equation (11) with respect to time as / dt, we obtain an equation that converts the acceleration at the vehicle center of gravity CG into the acceleration in the Earth coordinate system. JPEG0007669820000011.jpg48164

[0045] Acceleration of the vehicle's center of gravity CG a c is expressed by the following equation (17A), and the acceleration a w is expressed as the following equation (17B). JPEG0007669820000012.jpg3389

[0046] Acceleration of the vehicle's center of gravity CG a c , and the acceleration a at the rear wheel axle center 202 w By transforming equation (16) using the above relationship, we obtain the following equation (18), which can then be used to obtain equation (20) for variable conversion of acceleration. JPEG0007669820000013.jpg104164

[0047] The coordinate r of the rear wheel axle center 202 as seen from the vehicle center of gravity CG cw is r cw =[-l r , 0, 0], equations (13) and (20) are rearranged in the y (lateral) direction as follows to obtain equations (21) and (22). Equation (21) is a variable transformation equation for the lateral velocity of the vehicle body, and equation (22) is a variable transformation equation for the lateral acceleration of the vehicle body. JPEG0007669820000014.jpg13101 JPEG0007669820000015.jpg14122

[0048] Next, by substituting equations (21) and (22) into equation (8), the longitudinal velocity V at the center of gravity CG of the vehicle is calculated. c,x and the longitudinal speed V at the rear wheel axle center 202w,x are approximately equal, the following equation (23) is obtained. JPEG0007669820000016.jpg16164

[0049] As described above, in this embodiment, it is assumed that the rotational acceleration, which is the time derivative of the vehicle body yaw rate R, approximates 0. Furthermore, if it is assumed that the variation in road surface gradient is minute, it is considered that PQ, which is the product of the roll rate P and the pitch rate Q, approximates 0. As a result, the above equation (23) becomes the following equation (24). JPEG0007669820000017.jpg20164

[0050] In addition, the lateral acceleration output A of the IMU 26 at the rear wheel axle center 202 w,y is expressed by the following equation (25). JPEG0007669820000018.jpg12164

[0051] Where: JPEG0007669820000019.jpg1587 If so, equation (25) becomes equation (26) below. JPEG0007669820000020.jpg11164

[0052] From equations (24) and (26), the following equation (27) is obtained. JPEG0007669820000021.jpg24116

[0053] Therefore, the lateral velocity V w,y is expressed by the following equation (28). JPEG0007669820000022.jpg22105

[0054] And the slip angle β is β=V y / V x Therefore, it is expressed by the following equation (29). JPEG0007669820000023.jpg25126

[0055] As explained above, in this embodiment, the equations of vehicle motion are converted into variables seen from the rear wheel position, and attention is paid to the fact that the time derivative of the yaw rate, which is the turning angular acceleration, can be approximated to 0, and the product of the roll rate and the pitch rate can be approximated to 0 when the variation in the road surface gradient is small. As a result, the lateral speed is proportional to the vehicle speed and the lateral acceleration, and the slip angle is proportional to the lateral acceleration, and the proportionality coefficient in such a case is the normalized cornering stiffness C of the rear wheels. r This leads to the relationship shown in equations (28) and (29), which states that the force is the reciprocal of the product of the gravitational acceleration g and -2.

[0056] This embodiment is characterized in that the lateral speed can be easily calculated using only the normalized cornering stiffness independent of the vehicle mass, the gravitational acceleration, the lateral acceleration detectable by the IMU 26 or the like, and the wheel speed detectable by the vehicle speed sensor, as shown in equation (28). The slip angle can be calculated using only the lateral acceleration, normalized cornering stiffness, and gravitational acceleration, as shown in equation (29). In addition, due to the characteristics of the acceleration sensor such as the IMU 26, the influence of the gravitational acceleration caused by the inclination of the road surface can be taken into account without estimating the attitude angle, so that the lateral speed and slip angle can be calculated taking into account the attitude angle of the vehicle, even without determining the attitude angle of the vehicle.

[0057] In this embodiment, when deriving equations (28) and (29), the differential value of the lateral velocity is not approximated to zero and is included in the acceleration sensor term, so that the lateral velocity and slip angle can be calculated with high accuracy.

[0058] Estimating the position of a vehicle requires the lateral speed and slip angle of the vehicle. However, since the lateral speed and slip angle cannot be directly measured by sensors, they have been calculated by estimating the position based on steering angle data, using a number of physical parameters such as the vehicle mass and center of gravity position, and the cornering stiffness of the front and rear tires.

[0059] In addition, there have been cases where a Kalman filter or the like is used to estimate the vehicle's lateral speed by repeatedly comparing a predicted value estimated from an observation value detected by a sensor or the like with a new observation value to increase the accuracy of the predicted value.

[0060] However, when estimating the lateral speed and slip angle using a large number of parameters, there are problems in that the number of physical parameters is large, parameter adjustment is required for the estimation calculation, and the estimation result depends on the accuracy of each physical parameter. Also, there is a problem in that the calculation process of an algorithm such as a Kalman filter is complicated, and it is not easy to quickly calculate the lateral speed of the vehicle.

[0061] In this embodiment, by using the simple formulas shown in equations (28) and (29), the lateral speed and slip angle can be quickly derived, and rapid control, such as automatic driving, based on the derived lateral speed and slip angle can be achieved.

[0062] However, this embodiment is not limited to the above. The lateral velocity V at an arbitrary position a such as the center of gravity CG of the vehicle is expressed as follows: a,y The calculation of the lateral velocity V a,y To calculate, we use the same formula (30) as formula (11). wa =[x a ,y a ,z a ] is the position coordinate of an arbitrary position a as viewed from the rear wheel axle center 202. The position coordinate r of the position a wa Of which, x a is the coordinate value in the longitudinal direction of the vehicle 200 from the rear wheel axle center 202, and y a is the lateral coordinate value of the vehicle 200 from the rear wheel axle center 202, and z a is the vertical coordinate value of the vehicle 200 from the rear wheel axle center 202. JPEG0007669820000024.jpg17126

[0063] V a =dr waWhen equation (30) is rearranged in the same way as equation (13) with / dt, the following equation (31) is obtained. As shown in equation (31), the lateral velocity V at any position a a,y is not affected by the y component of the position coordinate of any position a as viewed from the rear wheel axle center 202. JPEG0007669820000025.jpg14126

[0064] In addition, the slip angle β at position a a is β a =V a,y / V a,x And the longitudinal velocity V at position a a,x and the longitudinal speed V at the rear wheel axle center 202 w,x If it is assumed that and are approximately equal, then it is expressed by the following formula (32). JPEG0007669820000026.jpg43155

[0065] In addition, the above equation (28) and the position coordinate r of the center of gravity CG of the vehicle as viewed from the rear wheel axle center 202 wc is r wc =[l r ,0,0], the lateral velocity at the vehicle center of gravity CG V c,y is expressed by the following equation (33). JPEG0007669820000027.jpg21126

[0066] As described above, according to this embodiment, the lateral speed and further the slip angle of each of the four wheels of the vehicle 200 can be calculated by using simple formulas such as those shown in equations (31), (32), and (33), respectively.

[0067] In this embodiment, the angular velocity of the vehicle body attitude angle detected by the IMU 26 is used, but is not limited to this. For example, the angular velocity of the vehicle body attitude angle may be calculated using a geomagnetic sensor, a GPS, or the like. Since the IMU 26, the geomagnetic sensor, the GPS, and the like are general-purpose sensors, the vehicle behavior calculation device 10 according to this embodiment can be widely mounted on a variety of mass-produced vehicles.

[0068] In this embodiment, the process executed by the CPU after reading the software (program) may be executed by various processors other than the CPU. In this case, examples of the processor include a PLD (Programmable Logic Device) such as an FPGA (Field-Programmable Gate Array) whose circuit configuration can be changed after manufacture, and a dedicated electric circuit such as an ASIC (Application Specific Integrated Circuit) which is a processor having a circuit configuration designed exclusively for executing a specific process. The process may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same or different types (for example, a plurality of FPGAs, a combination of a CPU and an FPGA, etc.). The hardware structure of these various processors is, more specifically, an electric circuit that combines circuit elements such as semiconductor elements.

[0069] In the present embodiment, the program is assumed to be pre-stored (installed) in the disk drive 50 or the like, but is not limited to this. The program may be provided in a form stored in a non-transitory storage medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. The program may also be downloaded from an external device via a network.

[0070] (Additional note 1) Memory, at least one processor coupled to the memory; Including, The processor, calculating a lateral speed at the rear axle center by multiplying a product of a lateral acceleration at the rear axle center of the vehicle detected by an acceleration detection unit and a longitudinal speed at the rear axle center detected by a vehicle speed detection unit by a predetermined proportionality coefficient; A vehicle behavior calculation device configured as above. [Explanation of symbols]

[0071] 10 Vehicle behavior calculation device 12 Input Devices 14 Arithmetic unit 16 Output Devices 18 Storage device 24 Vehicle speed sensor 26 IMU 200 vehicles 202 Rear wheel axle center CG vehicle center of gravity

Claims

1. an acceleration detection unit capable of detecting a lateral acceleration at a rear wheel axle center of a vehicle; a vehicle speed detection unit for detecting a longitudinal speed at a center of the rear wheel axle; a calculation unit that calculates a lateral speed at a center of the rear wheel axle by multiplying a product of the lateral acceleration detected by the acceleration detection unit and the longitudinal speed detected by the vehicle speed detection unit by a predetermined proportionality coefficient; Including, The predetermined proportionality coefficient is the inverse of the product of the normalized cornering stiffness of the rear wheels, the acceleration due to gravity, and −2. Vehicle behavior calculation device.

2. 2. The vehicle behavior calculation device according to claim 1, wherein the calculation unit calculates a slip angle at a center of a rear wheel axle of the vehicle by multiplying the lateral acceleration detected by the acceleration detection unit by the predetermined proportionality coefficient.

3. The acceleration detection unit is capable of detecting a roll rate and a yaw rate, which are angular accelerations of an attitude angle of the vehicle, 2. The vehicle behavior calculation device according to claim 1, wherein the calculation unit calculates the lateral velocity at the arbitrary position by adding, to the lateral velocity at the rear wheel axle center, the product of a yaw rate detected by the acceleration detection unit and a coordinate value of the vehicle in a longitudinal direction from the rear wheel axle center at the arbitrary position on the vehicle, and subtracting the product of a roll rate detected by the acceleration detection unit and a coordinate value of the vehicle in a vertical direction from the rear wheel axle center at the arbitrary position.

4. The acceleration detection unit is capable of detecting a roll rate and a yaw rate, which are angular accelerations of an attitude angle of the vehicle, 3. The vehicle behavior calculation device according to claim 2, wherein the calculation unit calculates the slip angle at the rear-wheel axle center by adding a value obtained by dividing the product of the yaw rate detected by the acceleration detection unit and a coordinate value of the vehicle in a longitudinal direction from the rear-wheel axle center at an arbitrary position on the vehicle by the longitudinal speed detected by the vehicle speed detection unit, and subtracting a value obtained by dividing the product of the roll rate detected by the acceleration detection unit and a coordinate value of the vehicle in a vertical direction from the rear-wheel axle center at the arbitrary position by the longitudinal speed detected by the vehicle speed detection unit, to the slip angle at the rear-wheel axle center.

Images